Sun Protection Sample SPF Test

The sun protection index of cosmetics is an important indicator of the effectiveness of cosmetic skin care, which is widely used in the cosmetics industry and is a very critical performance indicator. SPF is the abbreviation for sun protection factor, which is a performance indicator of sunscreen cosmetics to protect the skin from sun spots. The SPF value of sunscreen cosmetics often represents an indicator of the effectiveness of UVB protection.

What are the Ingredients of Chemical Sunscreen?

• In vitro testing

Commonly used in vitro testing methods are the UV spectrophotometer method and the SPF tester method. Based on the UVB-blocking properties of UVB absorbers and shielding agents in sunscreen cosmetics, the sunscreen is applied to a special tape, irradiated using different wavelengths of UVB, and then the absorbance of the sample is tested, and the sunscreen effect of the product is directly evaluated based on the size of the test value.

• Human body test

SPF human test method is the current international unified test method. The determination of SPF value in the test area is limited to the back between the waist and shoulder line, the subject's back skin should be divided into at least three zones:

• The first zone is directly irradiated with UV light.
• The second zone is irradiated with UV light after applying the test sample.
• The third zone should be irradiated with UV light after applying the SPF standard control.

The dose of UV radiation is increased in the following order, and the irradiated skin is subjected to different degrees of delayed erythema due to superficial vasodilation. The minimum amount of erythema (MED) of the subject's normal skin, i.e., the minimum dose or duration of UV exposure required for the appearance of clearly visible erythema at the irradiated site after 16 h ~ 24 h of UV exposure, is recorded as judged by a professionally trained evaluator.

The MED of the skin protected by the test sample must be performed on the same subject's test site and on the same day, and multiple products can be tested on the same subject's skin in one test.

Precautions for SPF Measurement

• Light source

• The light source output should be less than 1% of UV light with wavelength less than 290 nm after filtering by a filter.
• Light source output filtered by the filter, wavelength greater than 400 nm of ultraviolet light should be less than 5%.
• The light source should have a stable output with uniform light, and its fluctuation range should be less than 10% in the plane of radiation.

• Selection of subjects

• No previous history of photosensitive diseases and no recent use of drugs affecting photosensitivity.
• Subjects with skin type I, II, or III, i.e., sensitive to sunlight or UV radiation and prone to sunburn but not easily pigmented after exposure.
• The skin at the subject site should be free of hyperpigmentation, inflammation, scarring, pigmented nevi, hirsutism, etc.
• Persons who are pregnant, breastfeeding, taking anti-inflammatory drugs such as oral or topical corticosteroids, or who have undergone a similar test within the last month should be excluded from the subjects.

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